Datasheet

1200mA
500mA
700mA
1300mA
1000mA
300mA
ISYS
IBAT
IAC
1300mA current limit
Charge current setting
System load
Time
Time
Time
TPS65217A, TPS65217B, TPS65217C, TPS65217D
www.ti.com SLVSB64F –NOVEMBER 2011–REVISED APRIL 2013
Figure 9. Power Path Management. In this example the AC input current limit is set to 1300 mA, battery
charge current is 500 mA and system load is 700 mA. As the system load increases to 1000 mA battery
charging current is reduced to 300 mA to maintain AC input current of 1300 mA.
Detection thresholds for AC and USB inputs are a function of the battery voltage and three basic use-cases must
be considered:
Shorted or Absent Battery (V
BAT
< 1.5 V)
AC or USB inputs are valid and the chip powers up if V
AC
or V
USB
rises above 4.3 V. Once powered up, the input
voltage can drop to the V
UVLO
+ V
OFFSET
level (e.g. 3.3 V + 200 mV) before the chip powers down.
AC input is prioritized over USB input, i.e. if both inputs are valid, current is pulled from the AC input and not
USB. If both, AC and USB supplies are available, the power-path switches to USB input if V
AC
drops below 4.1 V
(fixed threshold).
Note that the rise time of V
AC
and V
USB
must be less than 50 ms for the detection circuits to operate properly. If
the rise time is longer than 50 ms, the IC may fail to power up.
The linear charger periodically applies a 10-mA current source to the BAT pin to check for the presence of a
battery. This will cause the BAT terminal to float up to > 3 V which may interfere with AC removal detection and
the ability to switch from AC to USB input. For this reason, it is not recommended to use both AC and USB
inputs when the battery is absent.
Dead Battery (1.5 V < V
BAT
< V
UVLO
)
Functionality is the same as for the shorted battery case. The only difference is that once AC is selected as the
input and the power-path does not switch back to USB as V
AC
falls below 4.1 V.
Good Battery (V
BAT
> V
UVLO
)
AC and USB supplies are detected when the input is 190 mV above the battery voltage and are considered
absent when the voltage difference to the battery is less than 125 mV. This feature ensures that AC and USB
supplies are used whenever possible to save battery life. USB and AC inputs are both current limited and
controlled through the PPATH register.
In case AC or USB is not present or blocked by the power path control logic (e.g. in OFF state), the battery
voltage always supplies the system (SYS pin).
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